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A pioneering technique which enables real time high quality passive acoustic monitoring (PAM) for mitigation during marine offshore industry operations-from anywhere in the world.

a new digital video-based visual monitoring system, that assists marine mammal mitigation by providing accurate, real-time sea surface distance estimation is described. Improvements on previous approaches are discussed and initial results from sea trials current taking place offshore are also presented.

Issues surrounding marine mammals and sound waves are technically complex, highly emotive, and not well understood, but it is a concern that must be addressed to ensure marine mammals are safeguarded. With this in mind, marine geophysical surveys implement mitigation measures. One important form of mitigation involves efforts to locate marine mammals within a prescribed area (frequently called the mitigation zone) surrounding air-gun arrays. These mitigation zones often extend to distances of 500 m from air-gun arrays. Independent marine mammal observers (MMO) visually monitor mitigation zones and operations are delayed or suspended when marine mammals are seen within the mitigation zone. Many marine mammals surface for no more than a few seconds at a time and can be difficult to see. Fog, precipitation, snow, and rough seas decrease the likelihood of visually detecting marine mammals, and visual monitoring is not as effective during hours of darkness. As a response to the need to better detect marine mammals in the vicinity of geophysical operations, passive acoustic monitoring (PAM) is sometimes utilized. PAM uses hydrophones to detect and localize vocalizations from marine mammals. PAM, like visual monitoring, may not detect all marine mammals, but it should improve detection rates. Unlike visual monitoring, it requires sophisticated hardware and software and its use for mitigation is not yet widely accepted.

Visual monitoring has been the primary method of detecting marine mammals during offshore operations for many years. The effectiveness of visual detection is reduced however, when animals are not at the surface and during periods of poor visibility. Towed passive acoustic monitoring (PAM) offers an opportunity to detect and indicate the location of marine mammal vocalisations relative to a hydrophone streamer being towed from a moving vessel. Vocalising marine mammal species may be identified by the characteristics of their calls and sonar clicks. Though basic automatic detection and species recognition functionality may be available, experienced and specialised operators are required to maximise detection/identification efficiency and minimise the likelihood of false detections. PAM is becoming an increasingly important monitoring tool during marine mammal population studies. When used as a monitoring tool in conjunction with mitigation measures, PAM provides the potential to reduce the risk of impacts from human activities on marine mammals. Though considered particularly useful for monitoring during periods of poor visibility, current towed PAM technology requires further development and field testing in order to provide a consistent and reliable real-time monitoring tool at sea. There is increased regulatory interest in using PAM as a means of monitoring marine mammals at sea during seismic survey operations at night or during periods of low visibility. As with any new technology, there is a need to ensure that both capabilities and limitations of the method during real-time Industry conditions are understood before requiring its use as a monitoring tool. Lessons learned from industry experience using PAM systems in the field will increase the understanding of current capabilities and limitations and will lead to further improvement of the technology. Recent experience of deploying towed PAM systems and testing a new; standardised user interface under real-time industry conditions, has identified some practical challenges of using PAM as a mitigation monitoring tool during offshore operations.